The cost of installing a conventional sewer system in a new parcel of land, whether its end use is residential, industrial or commercial, is one of the largest roadblocks to economic development for any community. Similarly, small or remote communities cannot afford the high price of adding a conventional sewer system even for residential usage and citizens continue to use private wells and inefficient septic systems.
Conventional sewer system installations cause significant disruption to a community and require major reconstruction of roadways. Individual dwellings are connected to a conventional sewer system through the use of large diameter rigid piping consisting of a series of connected pieces of pipe. The connections of these pipes are often leaky allowing infiltration of ground water which can account for up to 50% of a conventional sewage system's capacity. Leakage also results in exfiltration of sewage effluent. Moreover, the pipes must be deeply buried in areas of high frost penetration. Therefore, conventional sewer pipes require the digging of large, straight trenches approximately 6 to 8 feet deep. As well, the preferred and normal location of conventional systems is the roadway centerline. Conventional sewers therefore are timely to install and the choice of overall layout is dictated by access for maintenance.
Conventional systems are sensitive to gradient changes. Pipe gradients are steeper than prevailing road gradient to allow for the required high cleaning water velocities. The pipes must be kept in a straight alignment between manholes to aid maintenance and cleaning of the system.
The inclusion of ground water and high peaking factors in the design of pipes, pump stations, and treatment plants results in an overall conventional sewer system which is a large, complex system. Conventional sewer systems produce sludge at the treatment plants which must be removed regularly. Due to the short time it is in the system, there is little degradation of sludge and therefore high sludge volumes result. Lift pumps must be correspondingly large and complex in order to handle solids and high peak flows.
Therefore, there is a need to provide an efficient sewer system which is inexpensive to install and maintain. It should utilize flexible piping which does not need to be laid in straight alignment and which prevents infiltration of ground water and exfiltration of sewage. There is also a need for a sewage system which is not dependent on roadways and existing infrastructures for layout design.